1. Field of the Invention
This invention relates to an apparatus for driving the rollers of a roller hearth kiln which is used for making ceramic products such as for baking tile green ware.
2. Related Art Statement
In a conventional method for driving the rollers of a roller hearth kiln, a sprocket wheel is secured to the free end of each driving shaft of the roller and a long driving chain runs while engaging the sprocket wheels from above. In this method, the pitch of the driving chain must coincide with that of the sprockets. Even when they are in coincidence in the beginning, the driving chain is susceptible to an elongation after a long period of operation, and such elongation results in an increase of the driving chain pitch which leads to a difference in pitch between the driving chain and the sprockets. Difficulties have been experienced in that the driving chain tends to become afloat due to the above difference in pitch between the sprockets and the driving chain, and such floating of the driving chain is detrimental to accurate drive of the rollers.
Japanese Utility Model laid open Publication No. 9233/1972 proposed a modification of the roller driving apparatus. According to this modification, a continuous long case is provided on one side of the roller hearth kiln so as to house the sprocket wheels secured to the driving shafts of the rollers. Cushion rubber pieces are mounted on the lower surface of a top lid of the case in such a manner that each rubber piece urges the driving chain against the corresponding sprocket wheel so as to prevent the driving chain from getting afloat. However, the above modification has a number of shortcomings; namely, an additional load to the driving chain, difficulty in giving a proper tension to the driving chain, possibility of irregularity in roller rotation due to wear of the cushion rubber piece, and an increased complication in maintenance and repair such as removal of the top lid of the case which removal requires at least a partial stop of the roller hearth kiln.